1. FIELD OF THE INVENTION
The present invention relates to a process for the carboxylation of ethylene-vinyl acetate copolymers. More particularly, the present invention relates to a process in which carboxylic acid residues are incorporated into an ethylene-vinyl acetate copolymer such that the resultant product maintains the physical form of the original copolymer such as the powdered or pelletized form of the copolymer.
2. DESCRIPTION OF THE PRIOR ART
Ethylene-vinyl acetate copolymers have excellent properties of adhesiveness, melt flowability, toughness and softness. It has been known to introduce carboxylate group into ethylene-vinyl acetate so as to remarkably improve property. However, the chemical modification has been performed on ethylene-vinyl acetate copolymer by a method in which the reaction in conducted in the molten state and by a method in which the polymer is dissolved in a solvent and the reaction is performed in solution. No method is known in which the reaction can be conducted conveniently while maintaining the original form of the polymer, for example, as a powdered or pelletized material.
If carboxylation of a copolymer can be accomplished by a heterogeneous reaction in which the original powdered or pelletized form of the polymer is retained, such complicated steps which are inherent in the conventional solution method, as dissolution of the polymer before the reaction, separation of the carboxylated polymer and pelletization of the separated polymer, will become unnecessary. Such a method would have industrial advantages.